The invention relates to an eccentric screw machine, an eccentric screw motor or an eccentric screw pump for example, especially for sludgy media.
Eccentric screw machines are known from DE 102 45 497 B3 for example. They consist of a stator, which demonstrates a screw-shaped channel within which a screw-shaped rotor rotates. The screw-shaped channel defines a cross section which corresponds to a profile of an internal helical cut gearwheel. The cross section of the rotor corresponds to a pinion, which has one tooth less than the rotor. Together, the rotor and stator form chambers. When the rotor rotates, the center point of the cross section ideally moves on a circular path. Each cross section of the rotor thus executes an orbital movement around the longitudinal axis of the channel, the rotor also rotating around itself. Since the exterior surface of the rotor and the channel in the stator are both screw-shaped with the same direction of rotation, approximately banana-shaped hollows arise along the rotor advancing from one end of the stator toward the other end while the rotor is in motion. Other chambers, which are enclosed by other areas of the stator and other areas of the rotor, seal and separate each of these banana-shaped chambers. The stator is provided with an elastomeric lining to ensure a good seal between the separate chambers. To extend the temperature range of such eccentric screw pumps which are known in principle, the citation suggests that additional ribs, which run along the teeth, be mounted on the stator. The rotor elastically deforms these additional ribs, wherein they locally increase the surface pressure between the elastomeric lining and the rotor. The contact pressure between the rotor and stator can thereby be reduced overall. Moreover, the flexibility of the elastomeric lining is increased. In addition, space for accommodating material is created between the separate ribs, thereby improving the ability of the material to avoid the rotor.
Another eccentric screw pump, which is similarly constructed in principle, is known from EP 0 764 783 A1. However in place of continuous ribs on the elastomeric lining, there are provided finely structured projections in the shape of round heads, which are scaly and arranged one behind the other in rows. In this connection, the individual heads of one row are displaced relative to the heads of the adjacent row by approximately half the length of the heads of one row. Indentations, which separate the heads from one another, are located between the heads. This is intended to achieve a nonlinear impression characteristic of the individual projections, wherein the indentations located between the projecting parts are not formed as wide separation channels, but rather in such a manner that the pumped fluid or mash produces a lubricating effect that is not impaired when the fluid or mash is discharged. In particular, thusly designed eccentric screw pumps are supposed to require lower initial break-away torques during startup.
Eccentric screw machines of the above type are supposed to have a frictional resistance that is as low as possible during operation, wherein the chambers are supposed to be sealed relative to one another and wherein the wear of the elastomeric lining and/or the rotor is supposed to be low.